Related diphenylmethylene piperidine derivatives are known in the art. Notably, related compounds are disclosed in U.S. Pat. No. 4,540,780, and in a divisional thereof U.S. Pat. No. 4,666,905, mentioning diphenylmethylene piperidine derivatives which are useful as anti-emetic, anti-histamine, pulmonary, and antispasmodic agents.